Image capture device, including methods for arranging the optical components thereof

ABSTRACT

An image capture device includes a focusing lens, a light sensor array having a plurality of pixels arranged in a matrix of rows and columns and a plurality of optical components. Each optical component is configured to focus light on a light-sensing portion of one of the pixels. The locations of the optical components define a grid of parallel and perpendicular lines and a line spacing of the grid varies as a function of a distance from an optical axis of the focusing lens.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a non-provisional of, and claims the benefit of,co-pending, commonly assigned U.S. Provisional Patent Application No.60/608,972, entitled “FINE MICROLENS SHIFT” filed on Sep. 10, 2004,which application is incorporated herein by reference for all purposes.

This application is related to co-pending, commonly assigned, U.S.patent application Ser. No. 10/474,798, entitled “CMOS IMAGER FORCELLULAR APPLICATIONS AND METHODS OF USING SUCH”, filed on Oct. 8, 2003,which is a nationalization of International Patent Application No.PCT/US02/17358, entitled “CMOS IMAGER FOR CELLULAR APPLICATIONS ANDMETHODS OF USING SUCH,” filed on May 29, 2002, which application is anon-provisional of, and claims the benefit of, U.S. ProvisionalApplication No. 60/294,388, entitled “CMOS IMAGER FOR CELLULARAPPLICATIONS,” filed on May 29, 2001, the entire disclosure of each ofwhich are incorporated herein for all purposes. This application is alsorelated to the following co-pending, commonly assigned and concurrentlyfiled US Applications, the entirety of each of which is included hereinby reference: U.S. patent application Ser. No. ______, (Attorney DocketNumber 040013-002420US), entitled “AN IMAGE CAPTURE DEVICE, INCLUDINGMETHODS FOR ARRANGING THE OPTICAL COMPONENTS THEREOF”, and U.S. patentapplication Ser. No. ______, (Attorney Docket Number 040013-002440US),entitled “AN IMAGE CAPTURE DEVICE, INCLUDING METHODS FOR ARRANGING THEOPTICAL COMPONENTS THEREOF.”

BACKGROUND OF THE INVENTION

The present invention relates generally to systems and methods fordetecting and/or transmitting images. More particularly, the presentinvention relates to detecting and transmitting images in relation to acellular telephone.

Focusing lenses of mobile image capture devices, such as CMOS-baseddigital cameras, are often not telecentric. Telecentric lenses are oftentoo bulky for portable devices. Hence, a principle ray of the light ateach pixel of a sensor array is not normal to the surface of the pixel.Moreover, the further a pixel is from the center of the array, thegreater the angle of the principle ray varies from normal.

Pixels typically include a light sensor (e.g., photodiode or the like),a microlens that focuses incoming light on the light sensor, and a colorfilter. Pixels also may include one or more silicon dioxide layers,silicon nitride layers, planarization layers, and the like. Hence, thestackup of layers, which may have different refractive indexes anddifferent thicknesses, complicate the problem. Essentially, the lightmust be redirected down and into a hole formed by the pixel layers.

Additionally, pixels are not light sensing throughout. The lightsensitive portion of a pixel may be only a fraction of the pixel's area.Even if a microlens is positioned to focus light fully within the pixelarea, some of the light may fall off the light sensitive region, leadingto loss of signal. Further, the light may be obscured by metal wiringand the like as the light travels through the pixel.

Complicating the foregoing is the reality that production equipment,such as mask lithography equipment, is not infinitely variable. Theequipment typically has a finite tolerance that prevents exact locationof mask borders.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention provide a method of determining a locationof each of a plurality of optical components with respect to a pluralityof pixels comprised by an array. The method includes providing the arrayof pixels. The array is generally planar and the pixels are arranged incolumns and rows having a pitch. The method also includes providing afocusing lens having an optical axis normal to the array and placingeach of the plurality of optical components in relation to the opticalaxis and an associated pixel. The optical components are grouped intomatrices of adjacent optical components. Each matrix of opticalcomponents includes a first group having one or more of the opticalcomponents and a second group having one or more of the opticalcomponents. The optical components have a dimension. The dimension forthe first group is a first value. The dimension for the second group isa second value. The first and second values are different.

In some embodiments, each matrix has an average pitch and the averagepitch varies as a function of a radial distance of the matrix from theoptical axis. The average pitch may vary in a linear relationship withrespect to the optical axis. The optical components may be colorfilters. The optical components may be microlenses. Placing each of theplurality of optical components in relation to the optical axis and anassociated pixel may include determining a location of each of themicrolenses with respect to a location of one or more opticalobstructions within its associated pixel. The at least one of the one ormore optical obstructions may include metal wiring. The pixel array maybe an array of CMOS sensors. The optical components may be comprised byan image capture device. The image capture device may be a mobiletelephone.

In additional embodiments, a method of locating a plurality of opticalcomponents of an image capture device includes providing a focusing lensand providing an image sensor having an array of pixels having a pitch.The image sensor array is configured to capture an image focused by thefocusing lens. The method also includes providing a plurality of opticalcomponents arranged in relation to the pixels. The plurality of opticalcomponents are arranged in matrices of the optical components. Thematrices include optical components having at least two different sizes.

In some embodiments, the optical components are color filters. Theoptical components may be microlenses. The image sensor, opticalcomponents, and focusing lens may be comprised by an image capturedevice. The image capture device may be a mobile telephone. The arraymay be an array of CMOS sensors.

In still other embodiments, an image capture device includes a focusinglens and an image sensor having an array of pixels having a pitch. Theimage sensor array is configured to capture an image focused by thefocusing lens. The device also includes a plurality of opticalcomponents arranged in relation to the pixels. The plurality of opticalcomponents are arranged in matrices of the optical components and thematrices include optical components having at least two different sizes.

In some embodiments, the optical components are color filters. Theoptical components may be microlenses. The image capture device may be amobile telephone. The array may be an array of CMOS sensors.

In still other embodiments, a method of determining a location for eachof a plurality of microlenses with respect to each of a plurality ofpixels includes providing an image capture device having a focusing lensand a light sensor array comprising the plurality of pixels arranged ina matrix of rows and columns. Each microlens is configured to focuslight on a light-sensing portion of one of the pixels. The method alsoincludes determining a location of each of a first portion of theplurality of the microlenses along a diagonal axis of the pixel array.The diagonal axis is perpendicular to and intersects an optical axis ofthe focusing lens of the image capture device. The optical axis of thefocusing lens is coincident with a normal axis of the pixel array. Themethod also includes determining a location of each of a second portionof the plurality of microlenses relative to the locations of the firstportion of the plurality of microlenses along the diagonal axis. Thelocations of the microlenses define a grid of parallel and perpendicularlines. A line spacing of the grid varies as a function of a distancefrom the optical axis of the focusing lens.

In some embodiments, the line spacing decreases, across at least aportion of the array, as the distance increases. The line spacing maydecrease as the distance increases in finite increments. The finiteincrements may relate to a mask resolution. The line spacing mayincreases, across at least a portion of the array, as the distanceincreases. The line spacing may increase as the distance increases infinite increments. The finite increments may relate to a maskresolution. The first and second portions of the plurality of pixels maybe comprised by a first quadrant of the pixel array. The method mayinclude determining a location of each of a third portion of theplurality of pixels comprised by a second quadrant of the pixel array.The locations of the pixels of the second quadrant of the pixel arraymay be symmetrical, about the normal axis, with respect to the firstquadrant. The method also may include determining a location of each ofa fourth portion of the plurality of pixels comprised by third andfourth quadrants of the pixel array. The locations of the pixels of thethird and fourth quadrants of the pixel array may be symmetrical, aboutthe normal axis, with respect to the first quadrant. Each pixel mayinclude a first layer positioned between the light sensing portion ofthe pixel and the microlens. The line spacing may be a function of arefractive index and a thickness of the layer. Determining a location ofeach of a first portion of the plurality of the microlenses along adiagonal axis of the pixel array may include determining an equationthat relates the location of the microlens to a radial distance from thenormal axis, determining a polynomial of order X that approximates theequation, using the polynomial to calculate a location of eachmicrolens, and rounding the calculated location to a nearest increment.The increment may relate to a mask resolution used to produce the lightsensor array. The order X may be in the range 2 to 10. The order X maybe 3. The image capture device may be a mobile telephone. The array maybe an array of CMOS sensors.

In still other embodiments, an image capture device includes a focusinglens, a light sensor array comprising a plurality of pixels arranged ina matrix of rows and columns, and a plurality of optical components,wherein each optical component is configured to focus light on alight-sensing portion of one of the pixels. The locations of the opticalcomponents define a grid of parallel and perpendicular lines. A linespacing of the grid varies as a function of a distance from an opticalaxis of the focusing lens.

In some embodiments, the line spacing decreases, across at least aportion of the array, as the distance increases. The line spacing maydecrease in finite increments as the distance increases. The finiteincrements may relate to a mask resolution. The line spacing mayincrease, across at least a portion of the array, as the distanceincreases. The line spacing may increase in finite increments as thedistance increases. The finite increments may relate to a maskresolution. Each pixel may include a first layer positioned between thelight sensing portion of the pixel and the optical components. The linespacing may be a function of a refractive index and a thickness of thefirst layer. The first layer may be a color filter. Each pixel mayinclude a second layer positioned between the light sensing portion ofthe pixel and the optical components. The line spacing may be a functionof a refractive index and a thickness of the second layer. The secondlayer may be a silicon dioxide layer. Each pixel may include a thirdlayer positioned between the light sensing portion of the pixel and theoptical components. The line spacing may be a function of a refractiveindex and a thickness of the third layer. The third layer comprises apassivation layer. The image capture device may be a mobile telephone.The array may be an array of CMOS sensors.

In still other embodiments, a method of determining a location for eachof a plurality of microlenses with respect to each of a plurality ofpixels includes providing an image capture device having a focusing lensand a light sensor array comprising the plurality of pixels. Eachmicrolens is configured to focus light on a light-sensing portion of anassociated one of the pixels. The method also includes determining alocation of each of the microlenses with respect to the light-sensingportion of the associated pixel. Determining a location of each of themicrolenses includes determining a location of each of the microlenseswith respect to a relative illumination component of the focusing lensas a function of a distance from an optical axis of the focusing lens tothe light sensing portion of the pixel that is associated with themicrolens.

In some embodiments, the optical axis of the focusing lens is coincidentwith a normal axis of a plane comprising the plurality of pixels. Theimage capture device may be a mobile telephone. The array may be anarray of CMOS sensors.

In still other embodiments, a method of determining a location for eachof a plurality of microlenses with respect to each of a plurality ofpixels includes providing an image capture device having a focusing lensand a light sensor array comprising the plurality of pixels. Eachmicrolens is configured to focus light on a light-sensing portion of anassociated one of the pixels. The method also includes determining alocation of each of the microlenses with respect to the light-sensingportion of the associated pixel. Determining a location of each of themicrolenses includes determining a location of each of the microlenseswith respect to a principle ray angle as a function of a distance fromthe pixel associated with the microlens to an optical axis of thefocusing lens.

In some embodiments, the image capture device is a mobile telephone. Thearray may be an array of CMOS sensors. Determining a location of each ofthe microlenses may include determining a unique location for eachmicrolens relative to each associated pixel.

In still other embodiments, an image capture device includes a focusinglens, a light sensor array comprising a plurality of pixels arranged ina matrix of rows and columns, and a plurality of microlenses. Eachmicrolens is configured to focus light on a light-sensing portion of oneof the pixels. The locations of the microlenses define a grid ofparallel and perpendicular lines. A line spacing of the grid varies as afunction of a distance from an optical axis of the focusing lens.

In still other embodiments, a method of determining a location for eachof a plurality of microlenses with respect to each of a plurality ofpixels includes calculating a location for each microlens. Thecalculated location for at least one particular microlens places themicrolens off of a grid of possible locations. The grid of possiblelocations includes a matrix of locations determined by a resolutionincrement associated with production equipment. The method also includesrevising the location of the particular microlens to be on the grid andproviding an image capture device having a focusing lens and an array ofpixels comprising the plurality of microlenses. The locations of themicrolenses define a grid of parallel and perpendicular lines. A linespacing of the grid varies as a function of a distance from an opticalaxis of the focusing lens. A line spacing difference from row-to-row andcolumn-to-column is a multiple of the resolution increment.

In some embodiments, the line spacing difference between any twoadjacent column pairs is less than or equal to 1 resolution increment.The line spacing difference between any two adjacent row pairs may beless than or equal to 1 resolution increment.

In still other embodiments, a method of determining a location for eachof a plurality of color filters with respect to each of a plurality ofpixels includes calculating a location for each color filter. Thecalculated location for at least one particular color filter places thecolor filter off of a grid of possible locations. The grid of possiblelocations includes a matrix of locations determined by a resolutionincrement associated with production equipment. The method also includesrevising the location of the particular color filter to be on the gridand providing an image capture device having a focusing lens and anarray of pixels comprising the plurality of color filters. The locationsof the color filters define a grid of parallel and perpendicular lines.A line spacing of the grid varies as a function of a distance from anoptical axis of the focusing lens. A line spacing difference fromrow-to-row and column-to-column is a multiple of the resolutionincrement.

In some embodiments, the line spacing difference between any twoadjacent column pairs is less than or equal to 1 resolution increment.The line spacing difference between any two adjacent row pairs may beless than or equal to 1 resolution increment.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the figures which aredescribed in remaining portions of the specification. In the figures,like reference numerals are used throughout several figures to refer tosimilar components. In some instances, a sub-label consisting of a lowercase letter is associated with a reference numeral to denote one ofmultiple similar components. When reference is made to a referencenumeral without specification to an existing sub-label, it is intendedto refer to all such multiple similar components.

FIG. 1 depicts an image capture device according to embodiments of theinvention.

FIG. 2 depicts a schematic representation of a cross-sectional view of apixel of the imager capture device of FIG. 1.

FIG. 3 depicts a first method of placing microlenses with respect topixels according to embodiments of the invention.

FIG. 4 illustrates a microlens matrix according to embodiments of theinvention.

FIGS. 5 a and 5 b depict microlens mask arrangements according toembodiments of the invention.

FIG. 6 depicts a method of placing microlenses according to embodimentsof the invention.

FIGS. 7 a and 7 b depict filter mask arrangements according toembodiments of the invention.

FIG. 8 depicts a method of placing color filters according toembodiments of the invention.

FIG. 9 depicts a pixel of the image capture device of FIG. 1.

FIG. 10 depicts a cross-sectional view of the pixel of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention provide systems and methods for arrangingoptical components of image capture devices. An image capture deviceaccording to embodiments of the invention may be, for example, digitalstill cameras, video recorders, I/R devices and the like. Such devices,especially digital still cameras, may be dedicated devices or integralwith other electronic devices such as cell phones. In specificembodiments of the present invention, the image capture device is a cellphone camera having a CMOS imaging array.

Optical components include optical sensors, pixels, microlenses, colorfilters, focusing lenses, and the like. In specific embodiments, anon-telecentric lens is used as the primary focusing lens of a CMOSimage sensor integrated with a mobile phone. Photodiodes, located in thepixels of the image sensor pixel array, receive incident light andtransmit a corresponding electrical signal to circuitry that quantifiesand records the signal. The pixels include color filters to therebyallow a full color image to be captured. Microlenses located atop eachpixel improve the signal quality by more efficiently directing the lighttoward the photodiode.

According to embodiments of the invention, the microlenses and/or colorfilters are individually placed to optimize the signal created by theincident light. The microlenses and/or filters are arranged with respectto the light sensing portion of the pixel, the focusing lens, and metallines internal to the pixel, among other things.

FIG. 1 illustrates an exemplary image capture device 100 according toembodiments of the invention. The device 100 includes a focusing lens102 and an image sensor array 104. The image sensor array 104 includes aplurality of pixels 106. The focusing lens 102 focuses light 108emanating from or reflecting from a subject 110 onto the sensor array104. The light rays 112 focused by the lens 102 are not telecentric. Alight ray 112-1 normal to the lens 102 focused on a pixel 106-1 locatednear the center of the array 104 strikes the pixel 106-1 at an anglenormal to the array 104. On the other hand, a ray 112-2 strikes thepixel 106-2 located some radius from the center of the array 104 at anangle less than ninety degrees. Hence, the angle at which a principleray strikes a pixel is a function of the pixel's radial distance fromthe point at which the normal ray strikes the plane of the pixel.

FIG. 2 is a cross-sectional view of a pixel 106. The pixel 106 includesa microlens 202 that focuses light on a light sensor 204. The lightsensor 204 (e.g., photodiode, or the like), is located some distancefrom the microlens 202, the separation being a result of several layers206, each having a thickness and a refractive index. Layers may include,for example, one or more of each of the following: color filters,dielectric layers, planarization layers, silicon dioxide layers,passivation layers, and the microlens itself. As the principle ray 112travels through each layer 206, including the microlens 202, the ray isdeflected. The degree of deflection is a function of the thickness ofeach layer and its refractive index. Hence, br, the distance the lightsensor 204 must be located from the normal axis 208 of the microlens202, and/or color filter, is given by:${\delta\quad r} = {\sum\limits_{i = 1}^{n}{z_{i}{\tan\left( \alpha_{ii} \right)}}}$

Due to the design of the main focusing lens, the foregoing equation isnon-linear. The principle angle of the light incident on a pixel is anon-linear function of the radial distance of the pixel from the opticalaxis. This non-linear equation for locating the pixel optical componentswith respect to one another may be approximated with a linear equationhaving the form:δr_(lin)(r)=k_(δ) ·rIt then follows that, if the pixels are square with a pitch p, themicrolenses and color filters may be placed at a smaller pitch p_(ml)given by:p_(ml) =p·(1−k _(δ))

Placing microlenses with respect to their associated pixels iscomplicated by at least two different realities. First, the precisionwith which a microlens may be located may be limited. For example, masklithography may be limited to hundredths of a pixel's width. In an imagesensor array having hundreds of rows and columns, microlenses may notsimply be placed at a different, constant pitch with respect to thepixels, since the machine resolution constraints result in excessivegaps and/or overlaps.

In some embodiments, a better approximation of a linear shift isachieved by laying out matrices of pixels. For example, for a pixelpitch of 5 μm, a mask resolution of 10 nm, and a calculated microlenspitch p_(ml)=4.9923 μm, the closest microlens pitch permitted by themask is 4.99 μm. For an array having 400 pixels along half a diagonal,the microlens of the corner pixel will be off by 400*(4.9923-4.99)=0.92μm. Such variation can lead to severe signal loss (e.g., vigneting)and/or optical cross-talk (e.g., loss of color information) for thecorner pixel. To achieve a better approximation, microlenses and colorfilters may be arranged in matrices. In this example, a 4×4 matrix mayinclude three elements along the diagonal having a dimension of 4.99 μmand a fourth having a dimension of 5.00 μm. Hence, the average pitch forthe matrix is (3*4.99+5.00)/4=4.9925 μm, which is significantly closerto the calculated pitch of 4.9923 μm.

In other embodiments, a piecewise linear approach is used. FIG. 3illustrates an exemplary method 300 of placing microlenses with respectto pixels, according to such embodiments of the invention. Those skilledin the art will appreciate that the method 300 is merely exemplary andthat other methods according to other embodiments may have more, fewer,or different steps than those illustrated and described herein. Further,other methods according to other embodiments may traverse the stepsillustrated and described herein in different orders. The method 300will be described with respect to the pixel array 400 of FIG. 4. FIG. 4illustrates one quadrant 402 of the array 400, the upper right quadrantin this case.

Microlens and color filter locations are defined by mask patches formedby the horizontal and vertical lines dividing the quadrant 400. Maskpatches for color filters generally have no gaps between them, whilemicrolens mask patches typically have gaps with a minimum and a maximumallowable size. The method 300 may be used for either optical component,and although the quadrant 400 appears to apply to color filters sincegaps are not shown, those skilled in the art will appreciate that FIG. 4may apply to either. Due to radial symmetry, mask patches 404 along thediagonal 406 are square, the bottom-left patch being the center of thearray. Hence, determining the locations of all mask patches, accordingto the method 300, becomes a matter of locating the corners of the maskpatches along the diagonal. The method begins at block 302, at which apolynomial is fitted to the equation given above that relates δr to apixel's radial distance from the normal principle ray. In a specificembodiment, a third order polynomial is used, which has been determinedto provide sufficient approximation in most cases. Many other polynomialorders may be used, however. Hence, the polynomial has the form:δr_(poly) =a ₀ +a ₁ r ² +a ₃ r ³

At block 304, microlens mask patches 404 along the diagonal axes 406 arecalculated. At block 306, each calculated microlens mask patch border isrounded to the nearest mask resolution step. Due to radial symmetry, thecoordinate position of the upper right corner of each mask on thediagonal axis will fall on the axis.

The borders of each microlens mask patch 404 along the diagonal definehorizontal and vertical lines. These lines may be extended throughoutthe array to define the remaining mask patch locations. Hence, at block308, the borders of the microlens mask patches along the diagonal axis406 are used to create a grid of horizontal and vertical lines. Thelines define the locations of the remaining microlenses mask patches inthe array quadrant 402. At block 309, the locations of the microlenseswithin each patch are calculated. Then at block 310, the quadrant isreplicated to the remaining three quadrants of the array. In someembodiments, colors are assigned to pixels at block 312. Those skilledin the art will appreciate that the foregoing is but one exemplaryembodiment and will recognize other embodiments in light of thisdisclosure.

In other embodiments, microlens mask patches are individually located.This may be accomplished by “snapping” the calculated locations of themask patches to a grid of possible positions determined based on themask resolution. In some embodiments, as each X and Y coordinateposition of a mask patch corner are calculated, the positions arerounded to the nearest mask resolution increment. This may simplyinclude rounding the calculated X and Y coordinate locations to thesignificant figure that represents the mask resolution. This methodworks particularly well for mask resolutions in tenths of a significantfigure.

Individually locating mask patches, as opposed to locating them asdescribed above with respect to FIGS. 3 and 4, may require additionalconsiderations. For example, in some embodiments, microlens mask patcheshave a desired gap size between patches. Simply snapping the patches tothe grid may create excessively narrow gaps (or overlaps) or excessivelywide gaps. It therefore becomes necessary, in some such embodiments, toidentify and correct gap deviations that are out of the acceptablerange. FIGS. 5 a and 5 b illustrate the two possible situations in whichgap deviations may need correction. In FIG. 5 a, the pitch changes alongonly one direction. In FIG. 5 b, the pitch changes along bothdirections.

FIG. 5 a illustrates a row and column intersection 500 of microlens maskpatches appearing as squares 501, 502, 503, and 504 on a microlens mask.In this embodiment, we will assume that the “snapped” location of themask patch 504 caused it to encroach into the gap between it and themask patch 503 causing the gap to be too narrow. To accommodate this,the size of the patch 503 is reduced slightly. In other embodiments,however, the size of the mask may remain the same while the gap isreduced on one side or the other to account for the shift, provided, ofcourse, that the minimum and maximum gap size constraints are notviolated.

FIG. 5 b illustrates a situation in which a shift occurs both along therow and down the column. In this example, the sizes of the patches havebeen altered so that the gap remains constant.

FIG. 6 illustrates an exemplary method 600 of determining the microlensmask patch locations of FIGS. 5 a and 5 b according to embodiments ofthe invention. At step 602, the location of each microlens patch iscalculated using any of the previously-discussed equations for doing so.This may be accomplished, for example, by calculating the horizontal andvertical borders of each patch based on an ideal mask patch size. Itshould be pointed out that the calculated location may account for otherfactors, such as shading, as will be described with respect to FIGS. 9and 10.

At block 604, the microlens patch border locations are “snapped” to thenearest mask resolution increment. This may be accomplished by simplyrounding to the nearest mask resolution multiple. A pre-determinedoffset may be added if the starting point is taken to be some locationother than the exact center of the array.

In some cases, however, the final mask patch borders determined at block604 results in a gap of unacceptable width, either too large or toosmall. Hence, at block 606, column and row intersections are identifiedat which transitions occur that cause an unacceptable gap. Then at block608, mask patch borders are altered to maintain the proper gap size. Ina specific embodiment, this includes identifying the border nearest amask resolution increment to which the border could be relocated tomaintain the desired gap size. In some embodiments, this includesmaintaining constraints on the size of the resulting mask patch. Thosskilled in the art will appreciate may additional ways for accomplishingthis in light of this disclosure.

A similar process may be performed on mask patches used to createfilters, such as color filters. Unlike microlens mask patches, however,filter mask patches typically are gapless and snapping their locationsto the mask resolution grip will result in gaps and overlaps, both ofwhich must be corrected. Unlike microlens patches, however, filter maskpatches need not be rectangular. FIGS. 7 a and 7 b illustrate the twopossible column and row intersections that may occur in the placement offilters mask patches. The example of FIG. 7 a depicts a situation 700 inwhich a column border transitions by one mask resolution step. Colorfilters 702 and 703 are reduced in size to maintain the outer border ofthe region. No gaps or overlaps occur.

FIG. 7 b illustrates a situation 710 in which both a column and a rowtransition by one mask resolution step. In this situation, however, anoverlap would occur at the intersection. In this embodiment, the filterpatch 711 is altered to eliminate the overlap. The filter selected to beirregular may be the one having its border in the transition regionclosest to the mask resolution increment. The decision also may be madebased on color. Other embodiments are possible.

FIG. 8 depicts an exemplary method 800 for placing filter mask patchesaccording to embodiments of the invention. The method begins at block802 at which point filter mask locations are calculated using any of thepreviously-discussed equations for doing so. At block 804, filterborders not coincident with a mask resolution increment are “snapped” tothe nearest mask resolution increment. This is similar to the step 604for snapping the border locations of the microlens mask patchesdescribed previously. For example, this may be accomplished by roundingthe horizontal and vertical border location to the nearest maskresolution increment. Doing so, however, may create gaps and/oroverlaps, which may be unacceptable. Hence, at block 806 gaps andoverlaps are identified. Once gaps and overlaps are identified, at block808 the filter mask borders on either side of gaps may be expanded tothe mask resolution increment in the gap, if a mask resolution incrementis located in the gap. Otherwise, both borders are relocated to the maskresolution increment having the smallest cumulative difference. If thedifference is the same, then either mask resolution increment may bechosen. Or, a border may be chosen to avoid a situation as in FIG. 7 bin which both a column and row transition at the same intersection. Manypossibilities exist for properly adjusting the borders. For overlaps,the overlap region is assigned to one of the overlapping filters. Insome embodiments, the overlap region is assigned to the filter for whichthe overlap region represents the smallest percentage increase in size.In some embodiments, the overlap region is assigned based on color. Instill other embodiments, the overlap region is assigned using acombination of the two. Many other examples are possible.

As mentioned previously, a microlens' calculated location may be furtheradjusted due to shading. Shading is the difference of signal levelbetween the pixels that are situated at different geometrical positionsof the sensor. Shading originates from many factors. For example,characteristics of the main focusing lens 102, metal wiring in the pixelitself, and/or the like contribute shading.

FIG. 9 illustrates a pixel 900 according to embodiments of theinvention. The pixel includes metal wiring 902 that at least partiallyobscures the light-sensing region 912 at a lower depth of the pixelshown in the cross-sectional view of the pixel in FIG. 10.

According to some embodiments of the invention, the microlens 102 islocated such that the spot it casts falls within the largest circle thatcan be inscribed in the pixel without ensnaring metal wiring 902. Insome embodiments, the center of the spot is made to fall on the centerof the inscribed circle. In other embodiments, the center of the spot ismade to fall on the center of sensitivity of the light sensing region.Other examples exist and are apparent to those skilled in the art. Insome embodiments, the microlens' curvature, a controllable parameter, isadjusted to change the size of the spot. In fact, in some embodiments,the curvature of each microlens is a function of its radial distancefrom the center of the array.

It should be apparent, however, with reference to FIGS. 9 and 10 thatthe microlens 102 is not necessarily, physically located at the centerof the largest circle due to the depth of the pixel and the angle of theprinciple ray. The physical positioning of the pixel should account forthe vertical and lateral placement of the light sensing region of thepixel with respect to the microlens and the location in the pixel volumeitself of the metal lines.

The foregoing may be embodied in the following equations, the derivationof which may be found in previously-incorporated U.S. Provisional PatentApplication No. 60/608,972, wherein x_(cml) and y_(cml) are the x and ycoordinates of the center of the microlens, x and y are the coordinatesof the corner of the pixel (shown as (0,0) in FIG. 9), and δr(r) is thefunction describing the required deviation relative to the pixel:${x_{cml} = {x - \frac{{x \cdot \delta}\quad{r(r)}}{\sqrt{x^{2} + y^{2}}}}};\quad{y_{cml} = {y - {\frac{{y \cdot \delta}\quad{r(r)}}{\sqrt{x^{2} + y^{2}}}.}}}$

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Accordingly, the above description should not betaken as limiting the scope of the invention, which is defined in thefollowing claims.

1. A method of determining a location for each of a plurality ofmicrolenses with respect to each of a plurality of pixels, the methodcomprising: providing an image capture device having a focusing lens anda light sensor array comprising the plurality of pixels arranged in amatrix of rows and columns, wherein each microlens is configured tofocus light on a light-sensing portion of one of the pixels; determininga location of each of a first portion of the plurality of themicrolenses along a diagonal axis of the pixel array, wherein thediagonal axis is perpendicular to and intersects an optical axis of thefocusing lens of the image capture device, and wherein the optical axisof the focusing lens is coincident with a normal axis of the pixelarray; and determining a location of each of a second portion of theplurality of microlenses relative to the locations of the first portionof the plurality of microlenses along the diagonal axis, whereby thelocations of the microlenses define a grid of parallel and perpendicularlines, wherein a line spacing of the grid varies as a function of adistance from the optical axis of the focusing lens.
 2. The method ofclaim 1, wherein the line spacing decreases, across at least a portionof the array, as the distance increases.
 3. The method of claim 2,wherein the line spacing decreases as the distance increases in finiteincrements.
 4. The method of claim 3, wherein the finite incrementsrelate to a mask resolution.
 5. The method of claim 1, wherein the linespacing increases, across at least a portion of the array, as thedistance increases.
 6. The method of claim 5, wherein the line spacingincreases as the distance increases in finite increments.
 7. The methodof claim 6, wherein the finite increments relate to a mask resolution.8. The method of claim 1, wherein the first and second portions of theplurality of pixels are comprised by a first quadrant of the pixelarray, the method further comprising: determining a location of each ofa third portion of the plurality of pixels comprised by a secondquadrant of the pixel array, wherein the locations of the pixels of thesecond quadrant of the pixel array are symmetrical, about the normalaxis, with respect to the first quadrant.
 9. The method of claim 8,further comprising determining a location of each of a fourth portion ofthe plurality of pixels comprised by third and fourth quadrants of thepixel array, wherein the locations of the pixels of the third and fourthquadrants of the pixel array are symmetrical, about the normal axis,with respect to the first quadrant.
 10. The method of claim 1, whereineach pixel comprises a first layer positioned between the light sensingportion of the pixel and the microlens and wherein the line spacing is afunction of a refractive index and a thickness of the layer.
 11. Themethod of claim 1, wherein determining a location of each of a firstportion of the plurality of the microlenses along a diagonal axis of thepixel array comprises: determining an equation that relates the locationof the microlens to a radial distance from the normal axis; determininga polynomial of order X that approximates the equation; using thepolynomial to calculate a location of each microlens; and rounding thecalculated location to a nearest increment, wherein the incrementrelates to a mask resolution used to produce the light sensor array. 12.The method of claim 11, wherein the order X is in the range 2 to
 10. 13.The method of claim 11, wherein the order X is
 3. 14. The method ofclaim 1, wherein the image capture device comprises a mobile telephone.15. The method of claim 1, wherein the array comprises an array of CMOSsensors.
 16. An image capture device, comprising: a focusing lens; alight sensor array comprising a plurality of pixels arranged in a matrixof rows and columns; and a plurality of optical components, wherein eachoptical component is configured to focus light on a light-sensingportion of one of the pixels; whereby the locations of the opticalcomponents define a grid of parallel and perpendicular lines and whereina line spacing of the grid varies as a function of a distance from anoptical axis of the focusing lens.
 17. The image capture device of claim16, wherein the line spacing decreases, across at least a portion of thearray, as the distance increases.
 18. The image capture device of claim17, wherein the line spacing decreases in finite increments as thedistance increases.
 19. The image capture device of claim 18, whereinthe finite increments relate to a mask resolution.
 20. The image capturedevice of claim 19, wherein the line spacing increases, across at leasta portion of the array, as the distance increases.
 21. The image capturedevice of claim 20, wherein the line spacing increases in finiteincrements as the distance increases.
 22. The image capture device ofclaim 21, wherein the finite increments relate to a mask resolution. 23.The image capture device of claim 16, wherein each pixel comprises afirst layer positioned between the light sensing portion of the pixeland the optical component and wherein the line spacing is a function ofa refractive index and a thickness of the first layer.
 24. The imagecapture device of claim 23, wherein the first layer comprises a colorfilter.
 25. The image capture device of claim 16, wherein each pixelcomprises a second layer positioned between the light sensing portion ofthe pixel and the optical component and wherein the line spacing is afunction of a refractive index and a thickness of the second layer. 26.The image capture device of claim 25, wherein the second layer comprisesa silicon dioxide layer.
 27. The image capture device of claim 25,wherein each pixel comprises a third layer positioned between the lightsensing portion of the pixel and the optical component and wherein theline spacing is a function of a refractive index and a thickness of thethird layer.
 28. The image capture device of claim 23, wherein the thirdlayer comprises a passivation layer.
 29. The image capture device ofclaim 16, wherein the image capture device comprises a mobile telephone.30. The image capture device of claim 16, wherein the array comprises anarray of CMOS sensors.